Lanthanide-organic complexes based on polyoxometalates: Solvent effect on the luminescence properties

Homochiral Dodecanuclear Lanthanide "Cage in Cage" for Enantioselective Separation

It is extremely difficult to anticipate the structure and the stereochemistry of a complex, particularly when the ligand is flexible and the metal node adopts diverse coordination numbers. When trivalent lanthanides (Ln^III) and enantiopure amino acid ligands are utilized as building blocks, self-assembly sometimes yields rare chiral polynuclear structures. In this study, an enantiopure carboxyl-functionalized amino acid-based ligand with C₃ symmetry reacts with lanthanum cations to give a homochiral porous coordination cage, (Δ/Λ)₁₂-PCC-57. The dodecanuclear lanthanide cage has an unprecedented octahedral "cage-in-cage" framework. During the self-assembly, the chirality is transferred from the enantiopure ligand and fixed by the binuclear lanthanide cluster to give 12 metal centers that have either Δ or Λ homochiral stereochemistry. The cage exhibits excellent enantioselective separation of racemic alcohols, 2,3-dihydroquinazolinones, and multiple commercially available drugs. This finding exhibits a rare example of a multinuclear lanthanide complex with a dual-walled topology and homochirality. The highly ordered self-assembly and self-sorting of flexible amino acids and lanthanides shed light on the chiral transformation between different complicated artificial systems that mimic natural enzymes.

Photoluminescent polymer hydrogels with stimuli-responsiveness constructed from Eu-containing polyoxometalate and imidazolium zwitterions

Inorganic-organic co-assembly of anionic polyoxometalates (POMs) with zwitterions provides a facile way to fabricate functional soft materials. In this paper, a translucent, photoluminescent polymer hydrogel was fabricated from Weakley-type POM Na9EuW10O36 (EuW10) and polymerizable imidazole-type zwitterion 3-(1-vinyl-3-imidazolio)propanesulfonate (VIPS) via a one-step synthesis method. Detailed characterization indicated that the polymerization of double bonds in VIPS and electrostatic interactions between EuW10 and VIPS play important roles in the formation of the hydrogels. Additionally, the introduction of non-polymerizable zwitterions 3-(1-methyl-3-imidazolio)propanesulfonate (MIPS) or 3-(1-decyl-3-imidazolio)propanesulfonate (C10IPS) can improve the mechanical and luminous performances of the hydrogels. Especially, C10IPS with a long alkyl chain would more significantly alter the coordination environment of EuW10, and consequently resulted in a more efficient energy transfer process. Further investigations revealed that the chemical environment around the Eu3+ can be highly influenced by organic solvents with stronger coordination abilities than water molecules, such as acetone. The translucency and luminescence intensity of the hydrogels can be reversibly transformed after alternately immersing in acetone or H2O for several minutes. Our results provided a useful strategy for the fabrication of luminescent hydrogels by regulating the noncovalent interactions between POMs and zwitterions.

Inorganic open framework based on lanthanide ions and polyoxometalates with high proton conductivity

The development of new proton-conducting materials that are cost effective and have high proton conductivity and water stability is very important in fuel cell technology.

Single-molecule magnet behaviour in polynuclear assembly of trivalent cerium ions with polyoxomolybdates

An isopolyoxomolybdate-based POM is coordinated to trivalent cerium ions to afford a hybrid complex namely, [Ce(dmso)8][Ce(η2-NO3)2(dmso)4(α-Mo8O26)0.5][Mo6O19]. The original electrostatic environment created around the Ce(III) by its coordination to the isopolyoxomolybdate core induces complex single-molecule magnet behavior.

Co-sensitization promoted light harvesting with a new mixed-addenda polyoxometalate [Cu(C12H8N2)2]2[V2W4O19]·4H2O in dye-sensitized solar cells

[Cu(C₁₂H₈N₂)₂]₂[V₂W₄O₁₉]·4H₂O-doped TiO₂ composites were introduced into the dye-sensitized solar cells as co-sensitizers in N719-sensitized photoanodes to enhance the photoelectric conversion efficiency.

Crystal structures and spectral properties of two polyoxometalate-based inorganic-organic compounds from silver-azine building blocks with bis-bidentate and tridentate ligands

Two polyoxometalate-based inorganic-organic hybrid compounds constructed from silver(I)-L species and saturated Keggin type polyoxoanion, [Ag2L2(1)]2(SiMo12O40)·1.5DMF·0.5CH3OH⋅H2O 1 and [{Ag4L2(2)(DMF)5}(SiMo12O40)] 2 (L(1) = phenyl 2-pyridyl ketone azine, L(2) = 3-phenyltriazolo[1,5-a]pyridine), have been synthesized and structurally characterized by IR, UV, elemental analysis, XRPD and complete single crystal structure analyses, where the ligands L(1) and L(2) are bis-bidentate and tridentate azines synthesized with the same materials under different conditions. The structure of 1 exhibits a dinuclear double-helicate with [SiMo12O40](4)(-) anions as counter ions, where all of the Ag centers coordinate to bis-bidentate chelating ligands. Compound 2 displays a two-dimensional sheet formed by the Ag-organic infinite chains and the [SiMo12O40](4)(-) alternately arranged in a "rail-like" fashion. The luminescent properties of 1 and 2 in the solid state were investigated.

Heterodinuclear (Sm, Tb) lanthanide pivalates with heterocyclic N-donors: synthesis, structure, thermal behavior, and magnetic and photoluminescence properties

The PL color evidently changes from red at 300 K to bright green at 77 K.